The role of CuO in promoting photocatalytic hydrogen production over TiO2

Low cost semiconductor photocatalysts that can efficiently harvest solar energy to generate H2 from water or biofuels will be critical to future hydrogen economies. In this study, low cost CuO/TiO2 photocatalysts (CuO loadings 0-15 wt.%) were prepared, characterized and evaluated for H2 production from ethanol-water mixtures (80 vol.% ethanol, 20 vol.% H2O) under UV excitation. TEM, XRF, EDAX, EPR, Raman, TGA, XPS and Cu L-edge NEXAFS data showed that at CuO loadings <5 wt.%, Cu(II) was highly dispersed over the TiO2 support, possibly as a sub-monolayer CuO species. At higher loadings, CuO crystallites of diameter 1-2 nm were identified. The photocatalytic activity of CuO/TiO2 photocatalysts was highly dependent on the CuO loading, with 1.25 wt.% CuO being optimal (H2 production rate = 20.3 mmol g−1 h−1). Results suggest that sub-monolayer coverages of Cu(II) or CuO on TiO2 are highly beneficial for H2 generation from ethanol-water mixtures and support the development of a sustainable H2 economy.